He heads a federal government research team that's butted heads with climate skeptics and sometimes with the Bush administration. Dr. Hansen, who writes prolifically, is often called to testify before Congress. And last week he was tossing rhetorical darts at the Houghton Mifflin publishing company for what he calls "many gross errors" in a textbook used in colleges and Advanced Placement high school classes.

One chapter, written by conservative authors, states that "science doesn't know how bad the greenhouse effect is" and that global warming is "enmeshed in scientific uncertainty." While that may be literally true, it doesn't reflect the expert consensus. As a Boston Globestory observed:

A reporter for conservative watchdog group Business & Media Institute wrote:

Such critics do not dampen Hansen's dogged effort to reverse current temperature trends caused by heat-trapping greenhouse gases like carbon dioxide, which Hansen warns has reached the "tipping point" of 385 parts per million. As noted by news organization Agence France-Presse:

Claiming in the AFP article that "both the executive branch and the legislative branch are strongly influenced by special fossil fuel interests," Hansen is challenging those interests directly.

He recently wrote to the head of one of the nation's largest power companies, asking that they meet to discuss the role coal-fired plants play in global warming. A Washington Post article went on to say that: